There is a growing interest in performing exercises designed to shift the optimum length of peak tension in muscles. The magnitude of force that a muscle is capable of generating depends, at least partially, on its length, velocity, and innervation. The optimum length of peak muscle tension (the “optimum length”) refers to the length at which a muscle is capable of producing the highest level of tension. The optimum length of peak tension in muscles can be shifted to longer muscle lengths through emphasis on eccentric training. Furthermore, the emphasis on concentric exercise may foster the development of type II b fibers fast contracting muscle tissue. Eccentric exercise may refer to an exercise during which a muscle is simultaneously contracting and lengthening such that the muscle contraction resists the lengthening of the muscle. For example, during an eccentric contraction the force generated by the muscle is insufficient to overcome the external load on the muscle and, as a result, the muscle fibers lengthen. Eccentric contractions may be performed as a means of lowering a load gently rather than allowing it to drop. Concentric exercise may refer to an exercise during which a muscle is simultaneously contracting and shortening such that the muscle contraction causes the shortening of the muscle. For example, during a concentric contraction the force generated by the muscle is sufficient to overcome the external load on the muscle and, as a result, the muscle fibers shorten. Depending on the type of athletic activity intended to be subsequently performed, i.e. the specific sport or activity which an individual is exercising in preparation for, either concentric, eccentric, or even isometric exercises may be desired. Performing certain types of eccentric exercise as a means of positively affecting mechanical properties of muscle is of particular interest. After even a single session of eccentric exercise, the length-tension relationship of a muscle (or group of muscles) can be altered such that the highest level of tension is produced at a longer muscle length than prior to the exercise session. This phenomenon potentially has beneficial implications for the reduction of injury and increased athletic performance.
Regarding reduction of injury specifically, many researchers contend that athletes whom produce peak tension at shorter muscle lengths are more prone to injury. As an example, the biarticulate hamstring muscles have been studied in this regard due to the high prevalence of hamstring injuries in sports. During the late swing phase in running, the hamstring is actively stretched via the simultaneous actions of hip flexion and knee extension and, resultantly, the hamstring muscles experience high tensions at or near their greatest lengths. This makes the hamstrings highly susceptible to muscle strain injuries. However, the risk of such injuries can be reduced by shifting the optimum length of peak muscle tension such that the optimum length occurs at longer muscle lengths, and as previously discussed, such a result can be accomplished through eccentric exercises. Regarding improvement of athletic performance, researchers have contended that eccentric exercise results in greater passive muscle stiffness at longer lengths and that this increases potential force production before muscle failure.
Despite the known benefits of eccentric exercise, the availability of specialized equipment allowing for a single person to efficiently perform such exercises without the assistance of others is, so far as applicant is aware, under developed. In some situations eccentric exercises, e.g. heavy eccentric lifts, cannot be performed at all without multiple spotters. For example, the performance of heavy eccentric barbell squats is not apt for a single user to perform because a user may become “stuck” in the squatted position resulting in a heightened risk of injury.
Information relevant to attempts to address these problems can be found in the following: U.S. Pat. No. 8,388,499 B1 to Rindfleisch, dated Mar. 5, 2013, and fully incorporated by reference herein; U.S. Pat. No. 4,540,171 to Clark et al., dated Sep. 10, 1985, and fully incorporated by reference herein; and U.S. Pat. No. 5,397,287 to Lindfors, dated Mar. 14, 1995, and fully incorporated by reference herein.
For the foregoing reasons, there is a need for an exercise system for enabling a user to vary the effective muscle tension during the course of the performance of an exercise for shifting an optimum length of peak muscle tension. Accordingly, such an exercise system is disclosed herein.